A method of this type is disclosed in EP-A 0 629 081. In the case of the known method, the amplitudes of video signals which originate from two different successive frames are compared with one another. One of the two video signals is delayed in a delay device, so that the video signals are simultaneously present for processing at the inputs of a difference value and absolute value forming unit. From the measured values thus obtained, maxima are determined within suitable search windows, a minimum being determined in turn from the said maxima. In the case of unmoving pictures, the minimum obtained in this way corresponds to the sought peak value of the noise signal. If the video signal processed in this way is generated by scanning a film, the difficulty arises that the so-called film grain noise depends to a very great extent on the density of the RGB film layers. This is a consequence of the nonlinear gamma characteristic during the film processing. In the case of negative films, the film grain noise is reduced in dark regions, while the amplitude of the film grain noise is very much greater, in comparison therewith, in bright regions. With the known method, however, it is only possible to detect the smaller proportion of the film grain noise.